[Qemu-devel] [PATCH v6 2/6] BitmapLog: bitmap dump code

[Sanidhya Kashyap <sanidhya.iiith@gmail.com>]

Signed-off-by: Sanidhya Kashyap <sanidhya.iiith@gmail.com>
---

No functional change, except:
- naming convention i.e. QemuProcess has been changed to QemuDirtyBitmapUser.
- rectified mistakes in documentation in qapi-schema.json.
- removed acronyms

 hmp-commands.hx         |  16 ++
 hmp.c                   |  18 +++
 hmp.h                   |   1 +
 include/exec/cpu-all.h  |   5 +-
 include/sysemu/sysemu.h |   5 +
 migration.c             |  12 ++
 qapi-schema.json        |  37 +++++
 qmp-commands.hx         |  32 ++++
 savevm.c                | 378 ++++++++++++++++++++++++++++++++++++++++++++++++
 vl.c                    |  23 +++
 10 files changed, 526 insertions(+), 1 deletion(-)

diff --git a/hmp-commands.hx b/hmp-commands.hx
index f859f8d..d104232 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -1786,6 +1786,22 @@ STEXI
 show available trace events and their state
 ETEXI
 
+     {
+        .name       = "log_dirty_bitmap",
+        .args_type  = "filename:s,iterations:i?,period:i?",
+        .params     = "filename iterations period",
+        .help       = "dumps the memory's dirty bitmap to file\n\t\t\t"
+                      "filename: name of the file in which the bitmap will be saved\n\t\t\t"
+                      "iterations: number of times the memory will be logged\n\t\t\t"
+                      "period: time difference in milliseconds between each iteration",
+        .mhandler.cmd = hmp_log_dirty_bitmap,
+    },
+STEXI
+@item log_dirty_bitmap @var{filename}
+@findex log_dirty_bitmap
+dumps the writable working set of a VM's memory to a file
+ETEXI
+
 STEXI
 @end table
 ETEXI
diff --git a/hmp.c b/hmp.c
index 4d1838e..d067420 100644
--- a/hmp.c
+++ b/hmp.c
@@ -1318,6 +1318,24 @@ void hmp_device_del(Monitor *mon, const QDict *qdict)
     hmp_handle_error(mon, &err);
 }
 
+void hmp_log_dirty_bitmap(Monitor *mon, const QDict *qdict)
+{
+    const char *filename = qdict_get_str(qdict, "filename");
+    bool has_iterations = qdict_haskey(qdict, "iterations");
+    int64_t iterations = qdict_get_try_int(qdict, "iterations", 3);
+    bool has_period = qdict_haskey(qdict, "period");
+    int64_t period = qdict_get_try_int(qdict, "period", 10);
+    Error *err = NULL;
+
+    qmp_log_dirty_bitmap(filename, has_iterations, iterations,
+                         has_period, period, &err);
+    if (err) {
+        monitor_printf(mon, "log_dirty_bitmap: %s\n", error_get_pretty(err));
+        error_free(err);
+        return;
+    }
+}
+
 void hmp_dump_guest_memory(Monitor *mon, const QDict *qdict)
 {
     Error *err = NULL;
diff --git a/hmp.h b/hmp.h
index 4fd3c4a..0895182 100644
--- a/hmp.h
+++ b/hmp.h
@@ -94,6 +94,7 @@ void hmp_cpu_add(Monitor *mon, const QDict *qdict);
 void hmp_object_add(Monitor *mon, const QDict *qdict);
 void hmp_object_del(Monitor *mon, const QDict *qdict);
 void hmp_info_memdev(Monitor *mon, const QDict *qdict);
+void hmp_log_dirty_bitmap(Monitor *mon, const QDict *qdict);
 void object_add_completion(ReadLineState *rs, int nb_args, const char *str);
 void object_del_completion(ReadLineState *rs, int nb_args, const char *str);
 void device_add_completion(ReadLineState *rs, int nb_args, const char *str);
diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h
index f9d132f..4824d36 100644
--- a/include/exec/cpu-all.h
+++ b/include/exec/cpu-all.h
@@ -299,13 +299,16 @@ CPUArchState *cpu_copy(CPUArchState *env);
 
 /* memory API */
 
+/* global name which is used with both migration and bitmap dump */
+#define RAMBLOCK_NAME_LENGTH 256
+
 typedef struct RAMBlock {
     struct MemoryRegion *mr;
     uint8_t *host;
     ram_addr_t offset;
     ram_addr_t length;
     uint32_t flags;
-    char idstr[256];
+    char idstr[RAMBLOCK_NAME_LENGTH];
     /* Reads can take either the iothread or the ramlist lock.
      * Writes must take both locks.
      */
diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
index d8539fd..b5525ea 100644
--- a/include/sysemu/sysemu.h
+++ b/include/sysemu/sysemu.h
@@ -227,4 +227,9 @@ extern QemuOptsList qemu_net_opts;
 extern QemuOptsList qemu_global_opts;
 extern QemuOptsList qemu_mon_opts;
 
+/* migration vs dirty bitmap process */
+bool qemu_process_check(QemuDirtyBitmapUser user);
+void qemu_process_set(QemuDirtyBitmapUser user);
+const char *get_qemu_dirty_bitmap_user_as_string(void);
+
 #endif
diff --git a/migration.c b/migration.c
index 8d675b3..6a02b40 100644
--- a/migration.c
+++ b/migration.c
@@ -117,6 +117,7 @@ static void process_incoming_migration_co(void *opaque)
     } else {
         runstate_set(RUN_STATE_PAUSED);
     }
+    qemu_process_set(QEMU_DIRTY_BITMAP_USER_NONE);
 }
 
 void process_incoming_migration(QEMUFile *f)
@@ -317,6 +318,7 @@ static void migrate_fd_cleanup(void *opaque)
     }
 
     notifier_list_notify(&migration_state_notifiers, s);
+    qemu_process_set(QEMU_DIRTY_BITMAP_USER_NONE);
 }
 
 void migrate_fd_error(MigrationState *s)
@@ -326,6 +328,7 @@ void migrate_fd_error(MigrationState *s)
     s->state = MIG_STATE_ERROR;
     trace_migrate_set_state(MIG_STATE_ERROR);
     notifier_list_notify(&migration_state_notifiers, s);
+    qemu_process_set(QEMU_DIRTY_BITMAP_USER_NONE);
 }
 
 static void migrate_fd_cancel(MigrationState *s)
@@ -436,6 +439,15 @@ void qmp_migrate(const char *uri, bool has_blk, bool blk,
         return;
     }
 
+    if (!qemu_process_check(QEMU_DIRTY_BITMAP_USER_NONE) &&
+        !qemu_process_check(QEMU_DIRTY_BITMAP_USER_MIGRATION)) {
+        error_setg(errp, "Migration not possible, since %s "
+                   "is in progress.", get_qemu_dirty_bitmap_user_as_string());
+        return;
+    }
+
+    qemu_process_set(QEMU_DIRTY_BITMAP_USER_MIGRATION);
+
     s = migrate_init(&params);
 
     if (strstart(uri, "tcp:", &p)) {
diff --git a/qapi-schema.json b/qapi-schema.json
index 689b548..f96e959 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -3481,3 +3481,40 @@
 # Since: 2.1
 ##
 { 'command': 'rtc-reset-reinjection' }
+
+##
+# QemuDirtyBitmapUser
+#
+# @none: no other process is being executed besides a simple VM execution.
+#
+# @migration: migration process is going on.
+#
+# @bitmap-dump: bitmap dump process is being executed.
+#
+# Since 2.2
+##
+{ 'enum': 'QemuDirtyBitmapUser',
+  'data': [ 'none', 'migration', 'bitmap-dump' ] }
+
+##
+# @log-dirty-bitmap
+#
+# This command will dump the dirty bitmap to a file by logging the
+# memory for a specified number of times with a defined time difference
+#
+# @filename: name of the file in which the bitmap will be saved.
+#
+# @iterations: #optional number of times the memory will be logged. The
+# min and max values are 3 and 100000 respectively. 3 is the default value,
+# if the iterations parameter is not stated.
+#
+# @period: #optional time difference in milliseconds between each iteration.
+# The min and max values are 10 and 100000 respectively. 10 is the default
+# value if the period parameter is not stated.
+#
+# Since 2.2
+##
+{ 'command' : 'log-dirty-bitmap',
+  'data'    : { 'filename'      : 'str',
+                '*iterations'   : 'int',
+                '*period'       : 'int' } }
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 7658d4b..db0a8ed 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -3752,5 +3752,37 @@ Example:
 
 -> { "execute": "rtc-reset-reinjection" }
 <- { "return": {} }
+EQMP
 
+    {
+        .name       = "log-dirty-bitmap",
+        .args_type  = "filename:s,iterations:i?,period:i?",
+        .mhandler.cmd_new = qmp_marshal_input_log_dirty_bitmap,
+    },
+
+SQMP
+log-dirty-bitmap
+----------------
+
+start logging the memory of the VM for writable working set
+
+Arguments:
+
+- "filename": name of the file, in which the bitmap will be saved.
+
+- "iterations": #optional number of times, the memory will be logged.
+  The min and max values are 3 and 100000 respectively. 3 is the default value.
+
+- "period": #optional time difference in milliseconds between each iteration.
+   The min and max values are 10 and 100000 respectively. 10 is the default
+   value.
+
+Examples:
+-> { "execute": "log-dirty-bitmap",
+     "arguments": {
+         "filename": "/tmp/fileXXX",
+         "iterations": 3,
+         "period": 10 } }
+
+<- { "return": {} }
 EQMP
diff --git a/savevm.c b/savevm.c
index e19ae0a..19f7b0c 100644
--- a/savevm.c
+++ b/savevm.c
@@ -42,6 +42,9 @@
 #include "qemu/iov.h"
 #include "block/snapshot.h"
 #include "block/qapi.h"
+#include "exec/address-spaces.h"
+#include "exec/ram_addr.h"
+#include "qemu/bitmap.h"
 
 
 #ifndef ETH_P_RARP
@@ -1137,6 +1140,381 @@ void do_savevm(Monitor *mon, const QDict *qdict)
     }
 }
 
+/*
+ * Adding the functionality of continuous logging of the
+ * dirty bitmap which is almost similar to the migration
+ * thread
+ */
+
+enum {
+    LOG_BITMAP_STATE_ERROR = -1,
+    LOG_BITMAP_STATE_NONE,
+    LOG_BITMAP_STATE_ACTIVE,
+    LOG_BITMAP_STATE_CANCELING,
+    LOG_BITMAP_STATE_COMPLETED
+};
+
+typedef struct BitmapLogState BitmapLogState;
+static int64_t MIN_ITERATION_VALUE = 3;
+static int64_t MIN_PERIOD_VALUE = 10;
+static int64_t MAX_ITERATION_VALUE = 100000;
+static int64_t MAX_PERIOD_VALUE = 100000;
+
+struct BitmapLogState {
+    int state;
+    int fd;
+    int64_t current_period;
+    int64_t current_iteration;
+    int64_t iterations;
+    unsigned long *log_bitmap_array;
+    QemuThread thread;
+};
+
+/*
+ * helper functions
+ */
+
+static inline void log_bitmap_lock(void)
+{
+    qemu_mutex_lock_iothread();
+    qemu_mutex_lock_ramlist();
+}
+
+static inline void log_bitmap_unlock(void)
+{
+    qemu_mutex_unlock_ramlist();
+    qemu_mutex_unlock_iothread();
+}
+
+static inline void log_bitmap_set_dirty(ram_addr_t addr,
+                                        unsigned long *log_bitmap_array)
+{
+    long nr  = addr >> TARGET_PAGE_BITS;
+    set_bit(nr, log_bitmap_array);
+}
+
+static bool log_bitmap_set_status(BitmapLogState *b,
+                                  int old_state,
+                                  int new_state)
+{
+    return atomic_cmpxchg(&b->state, old_state, new_state);
+}
+
+/*
+ * inspired from migration mechanism
+ */
+
+static BitmapLogState *log_bitmap_get_current_state(void)
+{
+    static BitmapLogState current_bitmaplogstate = {
+        .state = LOG_BITMAP_STATE_NONE,
+        .log_bitmap_array = NULL,
+    };
+
+    return &current_bitmaplogstate;
+}
+
+/*
+ * syncing the log_bitmap with the ram_list dirty bitmap
+ */
+
+static void log_bitmap_dirty_bitmap_sync(unsigned long *log_bitmap_array)
+{
+    RAMBlock *block;
+    uint64_t counter = 0; /* 0 means log bitmap */
+    address_space_sync_dirty_bitmap(&address_space_memory);
+    QTAILQ_FOREACH(block, &ram_list.blocks, next) {
+        qemu_bitmap_sync_range(block->mr->ram_addr, block->length,
+                               log_bitmap_array, &counter);
+    }
+}
+
+static inline bool value_in_range(int64_t value, int64_t min_value,
+                                  int64_t max_value, const char *str,
+                                  Error **errp)
+{
+    if (value < min_value) {
+        error_setg(errp, "%s's value must be greater than %ld",
+                         str, min_value);
+        return false;
+    }
+    if (value > max_value) {
+        error_setg(errp, "%s's value must be less than %ld",
+                         str, max_value);
+        return false;
+    }
+    return true;
+}
+
+static inline void log_bitmap_close(BitmapLogState *b)
+{
+    log_bitmap_lock();
+    memory_global_dirty_log_stop();
+    log_bitmap_unlock();
+
+    g_free(b->log_bitmap_array);
+    b->log_bitmap_array = NULL;
+    qemu_close(b->fd);
+    b->fd = -1;
+}
+
+static bool log_bitmap_ram_block_info_dump(int fd, int64_t ram_bitmap_pages,
+                                           bool dump_blocks_info)
+{
+    int block_count = 0;
+    int block_name_length;
+    RAMBlock *block;
+    int ret;
+
+    if (qemu_write_full(fd, &ram_bitmap_pages, sizeof(int64_t)) < 0) {
+        return true;
+    }
+
+    if (dump_blocks_info) {
+
+        QTAILQ_FOREACH(block, &ram_list.blocks, next) {
+            block_count++;
+        }
+
+        ret = qemu_write_full(fd, &block_count, sizeof(int));
+        if (ret < sizeof(int)) {
+            return true;
+        }
+
+        QTAILQ_FOREACH(block, &ram_list.blocks, next) {
+            block_name_length = strlen(block->idstr) + 1;
+            ret = qemu_write_full(fd, &block_name_length, sizeof(int));
+            if (ret < sizeof(int)) {
+                return true;
+            }
+
+            ret = qemu_write_full(fd, &(block->idstr), sizeof(char) *
+                                  block_name_length);
+            if (ret < sizeof(char) * block_name_length) {
+                return true;
+            }
+
+            ret = qemu_write_full(fd, &(block->offset), sizeof(ram_addr_t));
+            if (ret < sizeof(ram_addr_t)) {
+                return true;
+            }
+
+            ret = qemu_write_full(fd, &(block->length), sizeof(ram_addr_t));
+            if (ret < sizeof(ram_addr_t)) {
+                return true;
+            }
+        }
+    }
+    return false;
+}
+
+static void log_bitmap_update_status(BitmapLogState *b)
+{
+    int s = b->state;
+    switch (s) {
+    case LOG_BITMAP_STATE_ACTIVE:
+    case LOG_BITMAP_STATE_CANCELING:
+    case LOG_BITMAP_STATE_ERROR:
+        log_bitmap_set_status(b, s, LOG_BITMAP_STATE_COMPLETED);
+    }
+    return;
+}
+
+static void *bitmap_logging_thread(void *opaque)
+{
+    /*
+     * setup basic structures
+     */
+
+    BitmapLogState *b = opaque;
+    int fd = b->fd;
+    int64_t current_ram_bitmap_pages, prev_ram_bitmap_pages;
+    size_t bitmap_size = 0;
+    unsigned long *temp_log_bitmap_array = NULL;
+    char marker = 'M';
+    int ret;
+
+    b->current_iteration = 1;
+    log_bitmap_set_status(b, LOG_BITMAP_STATE_NONE,
+                             LOG_BITMAP_STATE_ACTIVE);
+
+    current_ram_bitmap_pages = 0;
+    prev_ram_bitmap_pages = 1;
+
+    /*
+     *  start the logging period
+     */
+
+    /*
+     * need lock for getting the information about the ram pages.
+     * This does not change on acquiring the lock
+     */
+    log_bitmap_lock();
+    current_ram_bitmap_pages = last_ram_offset() >> TARGET_PAGE_BITS;
+    bitmap_size = BITS_TO_LONGS(current_ram_bitmap_pages) *
+                                sizeof(unsigned long);
+    b->log_bitmap_array = bitmap_new(current_ram_bitmap_pages);
+    if (b->log_bitmap_array == NULL) {
+        b->state = LOG_BITMAP_STATE_ERROR;
+        log_bitmap_unlock();
+        goto log_thread_end;
+    }
+
+    memory_global_dirty_log_start();
+    log_bitmap_dirty_bitmap_sync(b->log_bitmap_array);
+    log_bitmap_unlock();
+
+    /*
+     * sync the dirty bitmap along with saving it
+     * using the QEMUFile pointer.
+     */
+    while (b->current_iteration <= b->iterations) {
+        if (!runstate_is_running() ||
+            b->state != LOG_BITMAP_STATE_ACTIVE) {
+            goto log_thread_end;
+        }
+
+        /*
+         * Need to calculate the ram pages again as there is a
+         * possibility of the change in the memory
+         */
+        log_bitmap_lock();
+        current_ram_bitmap_pages = last_ram_offset() >> TARGET_PAGE_BITS;
+        if (current_ram_bitmap_pages != prev_ram_bitmap_pages) {
+            temp_log_bitmap_array = bitmap_new(current_ram_bitmap_pages);
+            if (temp_log_bitmap_array == NULL) {
+                b->state = LOG_BITMAP_STATE_ERROR;
+                log_bitmap_unlock();
+                goto log_thread_end;
+            }
+            log_bitmap_dirty_bitmap_sync(temp_log_bitmap_array);
+        } else {
+            log_bitmap_dirty_bitmap_sync(b->log_bitmap_array);
+        }
+        log_bitmap_unlock();
+
+        if (current_ram_bitmap_pages != prev_ram_bitmap_pages) {
+            prev_ram_bitmap_pages = current_ram_bitmap_pages;
+            bitmap_size = BITS_TO_LONGS(current_ram_bitmap_pages) *
+                                        sizeof(unsigned long);
+            if (b->log_bitmap_array) {
+                g_free(b->log_bitmap_array);
+            }
+            b->log_bitmap_array = temp_log_bitmap_array;
+            temp_log_bitmap_array = NULL;
+            if (log_bitmap_ram_block_info_dump(fd, current_ram_bitmap_pages,
+                                               true)) {
+                b->state = LOG_BITMAP_STATE_ERROR;
+                goto log_thread_end;
+            }
+        } else {
+            if (log_bitmap_ram_block_info_dump(fd, current_ram_bitmap_pages,
+                                               false)) {
+                b->state = LOG_BITMAP_STATE_ERROR;
+                goto log_thread_end;
+            }
+        }
+
+        ret = qemu_write_full(fd, b->log_bitmap_array, bitmap_size);
+        if (ret < bitmap_size) {
+            b->state = LOG_BITMAP_STATE_ERROR;
+            goto log_thread_end;
+        }
+
+        ret = qemu_write_full(fd, &marker, sizeof(char));
+        if (ret < sizeof(char)) {
+            b->state = LOG_BITMAP_STATE_ERROR;
+            goto log_thread_end;
+        }
+        g_usleep(b->current_period * 1000);
+        b->current_iteration++;
+        bitmap_zero(b->log_bitmap_array, current_ram_bitmap_pages);
+    }
+
+    /*
+     * stop the logging period.
+     */
+ log_thread_end:
+    log_bitmap_close(b);
+    log_bitmap_update_status(b);
+    qemu_process_set(QEMU_DIRTY_BITMAP_USER_NONE);
+    return NULL;
+}
+
+void qmp_log_dirty_bitmap(const char *filename, bool has_iterations,
+                          int64_t iterations, bool has_period,
+                          int64_t period, Error **errp)
+{
+    int fd = -1;
+    BitmapLogState *b = log_bitmap_get_current_state();
+    Error *local_err = NULL;
+
+    if (!runstate_is_running()) {
+        error_setg(errp, "Guest is not in a running state");
+        return;
+    }
+
+    if (!qemu_process_check(QEMU_DIRTY_BITMAP_USER_NONE) &&
+        !qemu_process_check(QEMU_DIRTY_BITMAP_USER_BITMAP_DUMP)) {
+        error_setg(errp, "Dirty bitmap dumping not possible, since %s "
+                   "is in progress.", get_qemu_dirty_bitmap_user_as_string());
+        return;
+    }
+
+    qemu_process_set(QEMU_DIRTY_BITMAP_USER_BITMAP_DUMP);
+
+    if (b->state == LOG_BITMAP_STATE_ACTIVE ||
+        b->state == LOG_BITMAP_STATE_CANCELING) {
+        error_setg(errp, "dirty bitmap dump in progress");
+        return;
+    }
+
+    b->state = LOG_BITMAP_STATE_NONE;
+
+    /*
+     * checking the iteration range
+     */
+    if (!has_iterations) {
+        b->iterations = MIN_ITERATION_VALUE;
+    } else if (!value_in_range(iterations, MIN_ITERATION_VALUE,
+                               MAX_ITERATION_VALUE, "iterations", &local_err)) {
+        if (local_err) {
+            error_propagate(errp, local_err);
+        }
+        return;
+    } else {
+        b->iterations = iterations;
+    }
+
+    /*
+     * checking the period range
+     */
+    if (!has_period) {
+        b->current_period = MIN_PERIOD_VALUE;
+    } else if (!value_in_range(period, MIN_PERIOD_VALUE,
+                               MAX_PERIOD_VALUE, "period", &local_err)) {
+        if (local_err) {
+            error_propagate(errp, local_err);
+        }
+        return;
+    }  else {
+        b->current_period = period;
+    }
+
+    fd = qemu_open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY, S_IRUSR);
+    if (fd < 0) {
+        error_setg_file_open(errp, errno, filename);
+        return;
+    }
+
+    b->fd = fd;
+    qemu_thread_create(&b->thread, "dirty-bitmap-dump",
+                       bitmap_logging_thread, b,
+                       QEMU_THREAD_JOINABLE);
+
+    return;
+}
+
 void qmp_xen_save_devices_state(const char *filename, Error **errp)
 {
     QEMUFile *f;
diff --git a/vl.c b/vl.c
index 95be92d..a858752 100644
--- a/vl.c
+++ b/vl.c
@@ -206,6 +206,8 @@ bool qemu_uuid_set;
 static QEMUBootSetHandler *boot_set_handler;
 static void *boot_set_opaque;
 
+int dirty_bitmap_user;
+
 static NotifierList exit_notifiers =
     NOTIFIER_LIST_INITIALIZER(exit_notifiers);
 
@@ -768,7 +770,27 @@ void vm_start(void)
 
     qapi_event_send_resume(&error_abort);
 }
+/*
+ * A global variable to decide which process will only
+ * execute migration or bitmap dump
+ */
+
+static QemuDirtyBitmapUser dbu = QEMU_DIRTY_BITMAP_USER_NONE;
+
+bool qemu_process_check(QemuDirtyBitmapUser user)
+{
+    return user == dbu;
+}
+
+void qemu_process_set(QemuDirtyBitmapUser user)
+{
+    dbu = user;
+}
 
+const char *get_qemu_dirty_bitmap_user_as_string(void)
+{
+    return QemuDirtyBitmapUser_lookup[dbu];
+}
 
 /***********************************************************/
 /* real time host monotonic timer */
@@ -4545,6 +4567,7 @@ int main(int argc, char **argv, char **envp)
     }
 
     if (incoming) {
+        qemu_process_set(QEMU_DIRTY_BITMAP_USER_MIGRATION);
         Error *local_err = NULL;
         qemu_start_incoming_migration(incoming, &local_err);
         if (local_err) {
-- 
1.9.1